Given the distinct characteristics of soil structure and the thermal effects arising from the electrical and thermal properties of seawater, investigating the temperature growth behavior of marine direct current grounding electrodes and perfecting design solutions are of great significance to guaranteeing the optimal and consistent operation of offshore wind energy direct current systems. This paper uses a method combining spatial finite element and time-domain finite difference to establish a finite element model of marine direct current electrode on the basis of circuit-electrical field-thermal field interaction; the model fully considers the influence of the temperature behaviors of seawater electro-thermal properties on the performance of the marine direct current grounding electrode, uses a circuit model to simulate the uneven current distribution phenomenon in each conductor segment, and combines the electric-thermal field coupling model to calculate the electric-thermal field distribution behaviors of the marine direct current electrode during the dissipation process. Finally, this model was verified, and the results showed that the algorithm and model proposed in this paper have a certain degree of accuracy.